Comments on: LHC Magnet Test Failure http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/ Random samplings from a universe of ideas. Fri, 21 Nov 2008 18:08:10 +0000 http://wordpress.org/?v=2.3.1 By: Edo http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26569 Edo Thu, 12 Apr 2007 21:36:26 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26569 By the way, we do have spares, at least for the most deteriorated magnet. About the other triplets - now know to all have the same shortcoming-, we are looking for an alternative to the replacement of the faulty piece - which would involve removing all triplets, bringing them to the surface and so on... By the way, we do have spares, at least for the most deteriorated magnet. About the other triplets - now know to all have the same shortcoming-, we are looking for an alternative to the replacement of the faulty piece - which would involve removing all triplets, bringing them to the surface and so on…

]]> By: Edo http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26570 Edo Thu, 12 Apr 2007 21:31:14 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26570 More pictures here: http://8teslas.free.fr/zenphoto/index.php?album=Triplet+incident More pictures here:
http://8teslas.free.fr/zenphoto/index.php?album=Triplet+incident

]]> By: Doo http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26574 Doo Sat, 07 Apr 2007 03:36:48 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26574 >>>>> Stephen Uitti on Apr 2nd, 2007 at 2:30 pm >>>>> So, does Fermilab have a couple extra >>>>>> months to find the Higgs first? Applauses transforming in ovation.! >>>>> Stephen Uitti on Apr 2nd, 2007 at 2:30 pm
>>>>> So, does Fermilab have a couple extra
>>>>>> months to find the Higgs first?

Applauses transforming in ovation.!

]]> By: Sam http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26573 Sam Thu, 05 Apr 2007 17:24:15 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26573 Looks like 'only the 9' it says final focus quads - but these would likely carry the most current (shorter focal lengths), probably resulting in a more serious quenching problem, that perhaps was not specificly tested for. Looks like ‘only the 9′ it says final focus quads - but these would likely carry the most current (shorter focal lengths), probably resulting in a more serious quenching problem, that perhaps was not specificly tested for.

]]> By: JoAnne http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26571 JoAnne Thu, 05 Apr 2007 01:00:03 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26571 I just heard that the experts now have a proposed fix which is under review. Assuming this fix passes the reviews, the remaining magnets of this type can be fixed, in the tunnel without having to be removed. The magnet that blew up obviously has to be replaced. Don't know if there are spares, or if Fermilab has to build another one, ASAP, from scratch. Nobody knows the impact on the schedule yet. I just heard that the experts now have a proposed fix which is under review. Assuming this fix passes the reviews, the remaining magnets of this type can be fixed, in the tunnel without having to be removed. The magnet that blew up obviously has to be replaced. Don’t know if there are spares, or if Fermilab has to build another one, ASAP, from scratch. Nobody knows the impact on the schedule yet.

]]> By: Ellipsis http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26575 Ellipsis Thu, 05 Apr 2007 00:36:58 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26575 Answering my question (#8), via a suggestion from a colleague!: Amount of stored energy in an LHC quadrupole ~= 7.8 x 10^5 J (from http://quench-analysis.web.cern.ch/quench-analysis/phd-fs-html/node12.html -- that is for an arc quad, but final triplet quads are probably of the same order of magnitude) He heat of vaporization = 82.9 J/mol .0224 m^3/mol (ideal gas @ STP, as it would quickly heat up to room temp) => ~200 m^3 of helium gas! = a major personnel hazard in the tunnel (oxygen displacement) if released via relief valves in the event of a quench. Answering my question (#8), via a suggestion from a colleague!:

Amount of stored energy in an LHC quadrupole ~=
7.8 x 10^5 J
(from
http://quench-analysis.web.cern.ch/quench-analysis/phd-fs-html/node12.html
– that is for an arc quad, but final triplet quads are probably of the same order of magnitude)

He heat of vaporization = 82.9 J/mol

.0224 m^3/mol (ideal gas @ STP, as it would quickly heat up to room temp)

=> ~200 m^3 of helium gas!

= a major personnel hazard in the tunnel (oxygen displacement) if released via relief valves in the event of a quench.

]]> By: Sean http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26572 Sean Thu, 05 Apr 2007 00:29:09 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26572 So where did you get that photo, anyway? Did you take it? It's a great shot, and I haven't seen anything as good elsewhere. I notice that <a href="http://www.nature.com/news/2007/070402/full/070402-3.html" rel="nofollow"><em>Nature</em> </a> borrowed it from us. So where did you get that photo, anyway? Did you take it? It’s a great shot, and I haven’t seen anything as good elsewhere. I notice that Nature borrowed it from us.

]]> By: cyrus biscardi http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26562 cyrus biscardi Wed, 04 Apr 2007 16:47:20 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26562 Looks like a squirm can failure to me Looks like a squirm can failure to me

]]> By: Ellipsis http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26561 Ellipsis Tue, 03 Apr 2007 19:55:43 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26561 I overheard (or rather got an e-mail forward) that the support structure for the inner triplets would have to be re-engineered. Would anyone (such as Cherrill, or another magnet engineer) happen to know why one couldn't just put 10-atmosphere relief valves on the cryo-lines, rather than re-engineering the support? I overheard (or rather got an e-mail forward) that the support structure for the inner triplets would have to be re-engineered. Would anyone (such as Cherrill, or another magnet engineer) happen to know why one couldn’t just put 10-atmosphere relief valves on the cryo-lines, rather than re-engineering the support?

]]> By: Cherrill, Magnet Engineer http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26566 Cherrill, Magnet Engineer Mon, 02 Apr 2007 23:57:28 +0000 http://blogs.discovermagazine.com/cosmicvariance/2007/03/31/lhc-magnet-test-failure/#comment-26566 To reply to "njim"'s quibble: All quadrupoles in accelerators are used to focus the beam. The millions of particles in a bunch travelling along an evacuated beamline tend to spread out as they repel their same-charged bunch-mates. So, every so-often we put a quadrupole to focus them to reduce their spreading; these "regular" quads do not focus the beam to a very small spot, that is the purpose of the final focus quads. The "triplet" of quads that suffered the accident at LHC were indeed a set of final focus quads that focus the beam to a very small spotsize at an interaction point where the 2 circulating-in-opposite directions proton beams collide. These triplets are of a different design from the approximately 400 quads used to focus the LHC beams as they travel around their circular path. I'm not sure what you meant by "correct the beam"? The term "correct" is usually applied to the function of dipole magnets which steer the particles in the beam so they change direction, and all move in one direction. Whereas a quadrupole affects the particles that are off-center, say left and right, and forces them towards the magnet's center from both sides, this action we call focusing. Hope this information will help your future quibbling about accelerator magnets. To reply to “njim”’s quibble:
All quadrupoles in accelerators are used to focus the beam. The millions of particles in a bunch travelling along an evacuated beamline tend to spread out as they repel their same-charged bunch-mates. So, every so-often we put a quadrupole to focus them to reduce their spreading; these “regular” quads do not focus the beam to a very small spot, that is the purpose of the final focus quads.

The “triplet” of quads that suffered the accident at LHC were indeed a set of final focus quads that focus the beam to a very small spotsize at an interaction point where the 2 circulating-in-opposite directions proton beams collide.

These triplets are of a different design from the approximately 400 quads used to focus the LHC beams as they travel around their circular path.

I’m not sure what you meant by “correct the beam”? The term “correct” is usually applied to the function of dipole magnets which steer the particles in the beam so they change direction, and all move in one direction. Whereas a quadrupole affects the particles that are off-center, say left and right, and forces them towards the magnet’s center from both sides, this action we call focusing.

Hope this information will help your future quibbling about accelerator magnets.

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